The present invention relates to a process for the preparation of emulsions of oils and/or gums and/or resins, which are preferably viscous. Its subject is more particularly a process for emulsifying (poly)isocyanates.
Furthermore, diisocyanates, especially alkylene diisocyanates (tolonates) and their derivatives of biuret type or their trimers are widely employed in the activity of paints and varnishes.
However, among the problems which remain unsolved to date, there is one that is particularly acute, namely the use of large quantity of organic solvent, the presence of which is considered to be toxic and detrimental to the environment.
This is why one of the aims of the present invention is to provide a process which makes it possible to obtain a stable dispersion of (poly)isocyanates in water.
Another aim of the present invention is to provide a monomer which permits (poly)isocyanate formulations in aqueous phase, with a view to responding to the progress in the techniques and regulations which tend to make the organic solvents disappear.
In order to solve this problem, there is already a description of the preparation of aqueous emulsions of oils, especially of high viscosity, by separate introduction in two different steps of two types of amphiphilic surface-active agents (which have different xe2x80x9cHLBxe2x80x9d values when this scale can be employed) into a conventional mixing apparatus.
However, these techniques are expensive in respect of energies and difficult to use. They demand mixing devices capable of giving high shears.
This is why one of the aims of the present invention is to provide a process which makes it possible to employ equipment which does not give high shears.
Another aim of the present invention is to provide a process which avoids high consumptions of energies.
Another aim of the present invention is to provide a process which makes it possible to obtain a narrow particle size distribution of particularly fine droplets.
We disclose a process for the preparation of aqueous emulsions of viscous phases based on preferably viscous, advantageously masked (poly)isocyanate oils and/or gums and/or resins, using a conventional mixing apparatus and not requiring the obligatory use of two types of surface-active agents.
Such a process makes it possible to prepare emulsions of advantageously masked (poly)isocyanate oils and/or gums and/or resins of completely controlled and relatively homogeneous particle size.
The process forming the subject of the invention is characterized in that a mixture consisting of the following is blended
100 parts by weight of an advantageously masked (poly)isocyanate(s) phase (A) of dynamic viscosity at 25xc2x0 C. which is at least equal to 3 Pa s, preferably at least equal to 30 Pa s, or of consistency at 25xc2x0 C. which does not exceed 2000, advantageously masked (poly)isocyanate(s) phase including at least one oil and/or at least one gum and/or at least one resin:
2 to 20 parts by weight, preferably from 3 to 15 parts by weight of water;
2 to 20 parts by weight, preferably from 3 to 15 parts by weight of at one least surface-active agent (B) or a combination of 0.5 to 10 parts by weight, preferably of 1 to 10 parts by weight of at least one surface-active agent (B) and of 2.5xc3x9710xe2x88x924 to 20 parts by weight, preferably of 0.001 to 15 parts by weight of at least one thickening water-soluble polymer (C) of molecular mass higher than 10,000 g/mole, preferably higher than 100,000 g/mole,
the said surface-active agent or mixture of surface-active agents exhibiting an ELB of at least 10 and the relative quantities of water and of constituent(s) (B) and optionally (C) being such that the viscosity or the consistency of the mixture of water+surface-active agent(s)+optional thickening water-soluble polymer(s) is close to or higher than one tenth of the viscosity or consistency of the advantageously masked (poly)isocyanate(s) phase (A), preferably close to or higher than the viscosity or consistency of the advantageously masked (poly)isocyanate(s) phase (A);
the said blending being carried out over a period and in shearing conditions which are sufficient to obtain an emulsion of xe2x80x9coil-in-waterxe2x80x9d type of particle size of the order of 0.1 to 5 micrometres, preferably of the order of 0.2 to 3 micrometres;
in that the mixture is then optionally diluted with water as a function of the desired solids content.
According to the invention a small scatter is obtained with a d90xe2x88x92d10 which is at most equal to 4, more generally to 1.5 micrometres, preferably to 1 micrometre.
For a good implementation of the invention the dynamic viscosity measurements are preferably carried out at 25xc2x0 C. with the aid of a Brookfield viscometer according to AFNOR standard NFT 76 102 of February 1972; the determination of the consistency may be performed by measuring the penetrability with the aid of a penetrometer, for example according to one of the standards AFNOR NFT 60 119, NFT 60 123, NFT 66 004, ASTM D 217, D 937, D 1321 and D 5.
As examples of advantageously masked (poly)isocyanate(s) (A) which can be used there may be mentioned-those consisting of:
polymethylene diisocyanates (generally xcfx89,xcfx89xe2x80x2), it being possible for the chain sequencing of the methylenes to be interrupted by an aromatic nucleus or by an oxygen,
the compounds originating from these derivatives to obtain a biuret, a dimer or a trimer.
it is appropriate to cite the prepolymer(s) of these products, which are formed by the reaction of isocyanate functional group(s) with a diol in proportions which define the number of the prepolycondensate units and ensures that virtually all of the end functional groups are isocyanates.
It is also possible to cite the compounds of addition of the above derivatives to polyols which have at least 3 alcohol functional groups.
The isocyanate functional groups are advantageously masked (this term is preferable to that of xe2x80x9cblockedxe2x80x9d, frequently employed in texts of Anglo-American sources or those culturally adapted thereto), and, thus, for two reasons, the isocyanate functional group has actually reacted so that it is no longer at all isocyanate and when they are xe2x80x9creleasedxe2x80x9d there is no certainty in any case that one passes through an isocyanate intermediate, secondly this masking is not absolute since properties similar to the isocyanate are gradually encountered again at certain temperature).
According to one of the most surprising methods of the present invention, it has been possible to demonstrate that the emulsion technique employed makes it possible to obtain stable emulsions of unmasked (poly)isocyanate(s).
The relative chemical instability of the isocyanates in the presence of phases containing water molecules not only has not prevented the formation of the emulsion whose physical stability is remarkable, but also appears to have been significantly reduced by the emulsification. It appears, to an extent which depends especially on the dilution, on the surface-active agents and on the emulsifiers, that the emulsion technique protects the (poly)isocyanates for a while from chemical decomposition.
Thus the advantageously masked (poly)isocyanate(s) may advantageously correspond to the following formula:
A(-NCOblock)pxe2x80x83xe2x80x83(Formula I)
where A denotes an organic backbone which has n free valencies, p being between 2 and 7 (closed interval) advantageously between 2 and 4 (closed interval);
where NCOblock denotes an isocyanate functional group which is advantageously masked (or protected) or otherwise.
It is appropriate to mention that the total number of carbons of the said monomer is advantageously between 10 and 100, preferably between 20 and 100, more preferably between 25 and 75.
The backbone A may be made up from a heavy polyamine (including anilines) which, for example, has a carbon number equal to at least 6 advantageously to 10, preferably to 15 [which is converted into isocyanate by the action of phosgene in a manner which is per se known].
The backbone A may also be that of the trimers and of the biurets.
Among the masking groups it is possible to choose groups containing mobile hydrogen whose pKa is at most equal to 14, advantageously to 12 preferably to 10 more preferably 8.
The higher the pKa, the more it is desirable that the masking agent should be volatile.
The masking agents are chosen so that the emulsion should be stable at its storage temperature.
Among the chemical functional groups capable of masking isocyanates, the following functional groups may be mentioned by way of examples, or rather of paradigm:
alcohols and thiols
oximes
hydroxylamines
acids
amides and imides
betadiketones
pyrazoles
The advantageously masked (poly)isocyanate(s) phase (A) may advantageously be chosen from the phases of the list hereinafter:
An oil and/or a gum and/or a resin containing a (poly)isocyanate group of viscosity of at least 3 Pa s, preferably of the order of 30 to 2,500 Pa s. Or of consistency of the order of 200 to 2,000.
A mixture of oil(s) and/or gum(s) and/or resin(s) containing a (poly)isocyanate group, mixture of viscosity at least equal to 3 Pa s, preferably of the order of 30 to 2,500 Pa s. Or of consistency of the order of 200 to 2,000.
A mixture of oil(s) and/or gum(s) and/or resin(s) containing advantageously masked (poly)isocyanate groups and of at least one solvent (or diluent) for the said oil and/or gum and/or resin, mixture of viscosity at least equal to 3 Pa s, preferably of the order of 30 to 2,500 Pa s. Or of consistency of the order of 200 to 2,000.
The surface-active agents (B) used may be nonionic of HLB higher than 10, preferably of the order of 10 to 20, anionic, cationic, zwitterionic or amphoteric of HLB higher than 10.
The nonionic surface-active agents may be chosen from alkoxylated fatty acids, polyalkoxylated alkylphenols, polyalkoxylated fatty alcohols, polyalkoxylated or polyglycerolated fatty amides, polyglycerolated alcohols and alphadiols, ethylene oxide-propylene oxide block polymers etc., as well as alkylglucosides, alkylpolyglucosides, sugar ethers, sugar esters, sugar glycerides, sorbitan esters, etc., and the ethoxylated compounds of these sugar derivatives exhibiting an HLB of at least 10.
The anionic surface-active agents may be chosen from alkali metal alkylbenzenesulphonates, monoalkyl sulphates, alkyl ether sulphates, alkylaryl ether sulphates, dialkylsulphosuccinates, alkyl phosphates, ether phosphates, etc., exhibiting an HLB of at least 10.
Among the cationic surface-active agents there may be mentioned aliphatic or aromatic fatty amines, aliphatic fatty amides, quaternary a monium derivatives, etc. exhibiting an HLB of at least 10.
Among the zwitterionic or amphoteric surface-active agents there may be mentioned betaines and their derivatives, sultaines and their derivatives, lecithins, imidazoline derivatives, glycinates and their derivatives, amidopropionates, fatty amine oxides, etc. exhibiting an ELB of at least 10.
The thickening polymers (C) are soluble in water to at least 50%; examples of thickening polymers. which may be mentioned are:
Those obtained by chemical synthesis, such as polyvinyl alcohols, polyethylene glycols, polyvinylpyrrolidones, alkali metal polyacrylates etc.
Those extracted from plants and optionally modified, such as carrageenates, alginates, methyl celluloses, hydroxypropyl celluloses, hydroxyethyl celluloses etc.
The relative quantities of water, of surface-active agent(s) and of optional thickening polymer(s) are functions of the viscosity of the advantageously masked (poly)isocyanate(s) phase including at least one oil and/or one gum and/or one resin containing a (poly)isocyanate group and of the nature of the (mixture of) surfactant(s) and of the nature of the (mixture of) optional thickening polymer(s).
In the absence of thickening polymer the weight ratio of water/water+surface-active agent(s) is, for example, of the order of 20/100 to 70/100, preferably of the order 25/100 to 60/100 so as to stabilize an emulsion of an advantageously masked (poly)isocyanate(s) phase consisting of an oil containing a (poly)isocyanate group of viscosity of the order of 30 Pa s to 500 Pa s, with the aid of a nonylphenol which has 9 or 10 ethoxy units as the only surface-active agent.
The use of an aqueous phase consisting of water and sodium dodecyl sulphate as the only surface-active agent, in a weight ratio of water/water+surface-active agent of 5/7 and containing from 0.5 to 2% of its weight of hydroxyethyl cellulose as thickening polymer, allows the stabilization of oils of viscosity of the order of 5 Pa s TO 30 Pa s.
It is preferable, above all when the isocyanates are not masked, to choose thickening agents and surfactants which are substantially inert towards the isocyanate functional groups under the conditions of manufacture of the emulsion, especially at the temperature at which the emulsion is made, and in the storage conditions.
The operation of emulsifying the advantageously masked (poly)isocyanate(s) phase may be carried out:
by the introduction of at least one oil and/or one gum and/or at least one resin+optional solvent(s)+optional (poly)isocyanate into a mixture of water+surface-active agent(s)+optional water-soluble polymer(s), the optional filler(s) being present in the aqueous mixture and/or introduced into the said mixture, and then blending at a temperature of the order of 10 to 50xc2x0 C. in mixers of the extruder type with single or multiple screw(s), turbine planet wheel mixers, static mixers, blade, screw and arm mixers;
or, preferably, by introduction of water into an oil(s) and/or gum(s) and/or resin(s) present in totality or partially [for example 50-90% of the total quantity of oil(s) and/or gum(s) and/or resin(s)]+optional solvent(s)+optional filler(s)+surface-active agent(s)+optional water-soluble polymer(s) mixture, then blending at a temperature of the order of 10 to 50xc2x0 C. in mixers of the extruder type with single or multiple screw(s), turbine planet wheel mixers, static mixers, blade, screw and arm mixers etc. The optionally remaining quantity of oil(s) and/or gum(s) and/or resin(s) being introduced into the mixture after the formation of the xe2x80x9coil-in-waterxe2x80x9d emulsion while the blending is maintained.
One of the advantages of the present invention lies in the use of equipment developing relatively low shears, in general at least equal to 102 but advantageously at most equal to 105 preferably to 104, more preferably around 103. These reference measurements are carried out in continuous pure water phase.
The emulsions of advantageously masked (poly)isocyanate oils and/or gums and/or resins obtained according to the process of the invention are particularly stable in storage; they can be very fine and monodisperse; their solids content may range from 25 (or less, depending on the intended application of the said emulsions) to 98%, it being possible for the adjustment of the solids content to be carried out by dilution.
It is possible to obtain emulsions with organic diluent contents which are as varied as possible; it is thus possible to obtain emulsions containing no organic diluents.
When it is desired to emulsify an unmasked tolonate, it is preferable that the solids content should be as high as possible in general at least higher than 3/4 advantageously than 9/10 preferably than 19/20.
According to the invention it is possible to obtain such emulsions either directly, for example at higher temperature, or by producing an emulsion with organic diluent, an emulsion which will be subsequently treated to evaporate the said organic diluents.
It is obvious that the organic diluents will have been chosen so that they are easily capable of being evaporated in presence of water.
These emulsions may be employed for the preparation of (poly)isocyanate-based compositions in virtually all their uses, etc.
The invention is also aimed at an emulsion of mixtures of the (poly)isocyanate(s) with the compounds which must be polycondensed with it, this being especially when the (poly)isocyanate(s) are masked.
In particular, these emulsions may be useful for, and usable in, paints.
The composition of the paints may also include a coloured base. Consisting of a pigment and of titanium oxide.
The aqueous phase advantageously contains soluble oligo- or poly-mers of polyol or polyol(poly)amine condensate or polyester-polyol type in sufficient quantity to permit the final polycondensation.
Either the condensation reactant(s) is liposoluble and in this case the emulsion is produced by introducing the said reactant(s) into the (poly)isocyanates phase (noncontinuous phase) or by emulsifying them separately and mixing the various emulsions in which the continuous phase is the aqueous phase; or the reactant(s) are water-soluble and can, with appropriate surface-active agents, be used as agent for diluting the aqueous phase (continuous phase).
These are the polyols usually employed during condensations with the common isocyanates.
Among the polyols it is possible especially to employ those which are mentioned in European Patent Application published under No. 0358979, especially when the isocyanates are not masked.
When the (poly)isocyanate(s) are masked, either phase may contain a xe2x80x9cdemaskingxe2x80x9d catalyst in an appropriate form which is known per se. Thus, according to an embodiment of the invention the composition additionally comprises a catalyst for deblocking the isocyanate functional groups. (cf. Journal of Applied Polymer Science xe2x80x9cCatalysis of the Isocyanatexe2x80x94Hydroxyl Reactionxe2x80x9d vol. IV, issue No. 11, p. 207, (1960), J. W. Britain).
These catalysts are known in themselves and are advantageously chosen from those which induce a temperature of release of the isocyanate functional groups which is at most equal to the usual temperature of the final operations of setting of the varnish or of the paint or of equivalents.
The release temperature induced by the catalysts is advantageously at least equal to approximately 100xc2x0 C.
It is appropriate to point out that the protecting groups are released more easily if the nitrogen of the protected isocyanate functional group is bonded to an unsaturated, especially aromatic, carbon, which may sometimes be a drawbacks.
In the coating application it is preferable that the nitrogen of the protected isocyanate functional group should be bonded to a saturated carbon (sp3 hybridization). In the case where the isocyanates are not masked;[sic] such isocyanates bonded to a saturated carbon (sp3 hybridization) resist hydrolysis well especially in the case where the said carbon is secondary and preferably tertiary.
The backbone A may also be that of the trimers and of the biurets.
The mean size of the droplets is advantageously between 0.01 xcexcm and 20 xcexcm, preferably between 0.1 xcexcm and 10 xcexcm.
The examples are given by way of indication and cannot be considered as a limit of the field and of the spirit of the invention.
Definition
The Tolonate employed here is the product of the trimerization of hexamethylene diisocyanate
[Lacuna]
The tolonate D2 is the product of the trimerization of hexamethylene diisocyanate advantageously masked with methyl ethyl ketoxime and diluted with an aromatic petroleum fraction [Solvesso 100 (registered trademark)] until the latter reaches 25% by volume.